Abstract
The compressed air electric ratio (CAER) describes the ratio of the real electric power demand to the nominal mechanical power of an air compressor. The CAER is an important indicator as the electric power demand of air compressors varies throughout its operation dependent on compressor technology, pressure ratio, and free air delivery. The nameplate power of the compressor drive motor is not sufficient for evaluating the electric power demand; therefore, the CAER plays an important role in assessing the electric operating power demand. In this paper, results from measurements of fixed speed and variable speed (VFD) compressors are presented with the analysis of key influencing factors of the CAER. The data show that the pressure ratio of operating pressure to the maximum design outlet pressure has the largest impact on the CAER. For VFD compressors, the CAER is represented as a linear function dependent on the respective load. Fixed and variable speed compressors’ CAERs are always dependent on the load condition. In idle condition, the CAER was measured to be 0.2. In full load condition with a pressure ratio of 0.6, the CAER averages at a value of 0.87, meaning a 90 kW compressor at 0.6 pressure ratio draws 78.3 kW electric power.
Highlights
Compressed air as an energy source and its corresponding compressor systems are used in almost every industrial branch
The analyzed air compressors are located at the University of Stuttgart as well as in different companies throughout the mechanical engineering branch
The analysis shows that the compressed air electric ratio (CAER) for fixed-speed and VFD compressors can provide interesting insights
Summary
Compressed air as an energy source and its corresponding compressor systems are used in almost every industrial branch. In the glass industry, it is used at four bar gauge to shape the respective form of various glass jars by blowing the compressed air into a mold where the liquid glass is formed [1]. Other applications are in the plastic industry where it conducts various tasks such as transportation of the granules, controlling of cutting processes, or locking of casting molds [2]. The handling or controlling of production processes uses compressed air for a wide range of pneumatic applications. The minimum configuration of a compressed air system is the compressor itself, some kind of distribution system such as hoses or pipes, and a consumer. Companies install additional equipment for drying, filtration, storage, valves, or controls to meet the respective requirements
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